A variety of video imaging systems have been proposed for use on-board vehicles to monitor the driver and/or passenger(s) in the vehicle. Some proposed video imaging systems include one or more cameras focused on the driver of the vehicle to capture images of the driver's face. The images are processed to determine various facial characteristics of the driver including position, orientation, and movement of the driver's eyes, face, and head. Given the determined driver facial characteristics, such as the driver's eye positioning and gaze, vehicle control systems can provide enhanced vehicle functions.
One proposed vehicle control system can monitor one or both eyes of the driver and determine a condition in which the driver appears to be drowsy, and can initiate a countermeasure. Another proposed vehicle control system can also determine if the driver is distracted, and can act to minimize the distraction. Further, vehicle control systems can monitor the driver's eye gaze and control various vehicle systems, such as the radio and entertainment system, to provide enhanced control of such systems based on eye gaze monitoring.
In order to maximize the effectiveness of a vehicle imaging system during low ambient light conditions, such as night time operation, active light illumination may be required. Proposed approaches for illuminating the driver's face with light have included providing a light source generally focused on the driver's eye(s). Other proposed techniques for illuminating the driver's face employ multiple light sources at different wavelengths, arranged in a generally concentric ring, for generating a bright eye pupil and dark eye pupil effect. A further approach provides first and second light sources located on opposite sides of the camera to achieve light and dark eye pupil effects. One example of the aforementioned approach is disclosed in U.S. application Ser. No. 10/705,541, filed on Nov. 11, 2003, which is hereby incorporated herein by reference.
Many conventional approaches that employ active light illumination suffer from drawbacks. In particular, when the illuminated subject passenger is wearing corrective lens eye glasses, the geometry of the corrective lenses of the eye glasses may reflect the infrared illumination therefrom onto the image acquired by the imaging camera. This reflection of the illumination source is generally seen as a glare on the subject's eye glasses. The resultant glare may occur at the regions of interest near the eye(s) of the subject, thus inhibiting the ability to recognize imaged features.
Relocation or repositioning of the light illumination source may modify appearance and location of the resultant glare; however, the optical advantage of the curvature of the corrective lenses generally imposes that a large relocation distance of the illuminator provides only a minor adjustment in the resultant position of the glare on the lenses. Thus, relocation of the illuminating source, particularly in a vehicle, may not adequately mitigate the disruptive glare. The glare problem is further aggravated in that nominal movements of the subject's head may shift the glare so that the glare again occludes the eye. In a vehicle eye monitoring system, nominal head movements should not result in interruption of the subject monitoring.
It is therefore desirable to provide for an effective method of actively illuminating the eye(s) of a subject person and generating images of the eye(s) to allow for enhanced eye monitoring, particularly for a person wearing corrective lens glasses in a vehicle. In particular, it is desirable to provide for a more cost effective system and method that minimizes or eliminates glare that may result from a reflection from a reflecting surface, such as a corrective lens.